A hurricane warning was issued for the Texas coast Thursday morning, covering an area from Port Mansfield to Matagorda.

The storm's maximum sustained winds had increased to near 60 mph (95 kph). The U.S. National Hurricane Center said additional strengthening was expected and Harvey could become a hurricane by Friday, when it's expected to approach the southern Texas coast.

As of 8 a.m. EDT, the storm was centered about 335 miles (540 kilometers) southeast of Port Mansfield and was moving north-northwest near 10 mph (17 kph).

Emergency officials Wednesday asked residents along the upper Texas coastline to move or prepare to move inland. Those in low-lying areas were urged to seek higher ground, and those elsewhere were told to monitor official announcements closely.

On South Padre Island, people filled sandbags and loaded them into cars and vans Wednesday to take to protect exposed homes and businesses. Others in the forecast path of the storm sought out generators, plywood and other goods from hardware stores. Meanwhile, rice farmers in coastal Matagorda County moved quickly to harvest their crops.